Specify exact dependency requirements

[qstokkink]

Our requirements.txt file mostly does not specify what the minimum version is we support for each dependency. We should make this more explicit to avoid preventable failures.

I ran an automated test to check which of the available versions of our dependencies managed to (1) install on my Windows 10 machine and (2) pass our unit tests. The results are as follows (green passed, red failed either step 1 or 2):

[qstokkink]

For reference, this is the script I used https://gist.github.com/qstokkink/4e99ff4bc19266b27f7c942dfba3a58d

[qstokkink]

Upon further reflection: when installing the latest version of its dependencies IPv8 should just work. If a dependency becomes a problem (for whatever reason) we can treat the issue on a case-by-case basis (e.g., how we phased out asyntest).

Managing a huge matrix of supported versions is overkill for our project's scope and I'll close this issue.